This study investigated whether L1 background and visual information impact the effectiveness of skewed and balanced input at promoting pattern detection. Participants (N= 84) were exposed to Esperanto sentence with the transitive construction under skewed (one noun with high token frequency) or balanced input (equal token frequency) conditions while viewing either colour or black and white visuals. Their ability to detect the relevant morphological and syntactic features of the transitive construction was tested through a forced judgement task using novel nouns. The results indicated no significant main effect for  visual information or input type. There was, however, a significant main effect for L1 on learners’ capacity to notice the accusative inflection in Esperanto. The implications are discussed in terms of the effect of L1- specific transitive encodings on speakers’ ability to abstract a novel transitive construction.